Transcript Fig. 2.17. Conventional symbols used in depicting human pedigrees.

propositus
person initiating the study
expressivity variation in phenotype
penetrance if phenotype  genotype

Fig. 2.17. Conventional symbols used in
depicting human pedigrees.
© 2006 Jones & Bartlett Publishers
Pedigrees can be used to follow transmission routes
(who got it from whom)
Can sometimes be used to determine type of transmission
(autosomal or X-linked)
(dominant or recessive)
New (spontaneous) mutations would be difficult to interpret
© 2006 Jones & Bartlett Publishers
p
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Autosomal recessive:
both sexes affected equally
most affected people have unaffected parents
about 1/4 of children of a pair of carriers would be affected
if two affected individuals reproduce all offspring will be affected
Autosomal dominant:
both sexes affected equally
affected people have at least one affected parent
about 1/2 of children of a affected person would be affected
(most affected people are heterozygous)
X-linked (sex-linked) recessive:
males show trait more than females
in families: often grandfather to grandson transmission
all affected females have affected fathers
X-linked (sex-linked) dominant:
more common in females than males
every affected person has at least on affected parent
daughters of affected males will be affected
females pass it on to half of their children
(assuming they are heterozygous)
Most human genetic disease are “rare.”
If too many unrelated people have to be carriers…
…probably the wrong mode of inheritance.
http://www.blackwellpublishing.com/korfgenetics/figure.asp?chap=03&fig=Fig3-10
XD Y
Xd Xd
Xd Y
XD Xd
X-linked
recessive
or
or
autosomal ?
dominant
http://www.blackwellpublishing.com/korfgenetics/figure.asp?chap=03&fig=Fig3-10
i
iii
ii
autosomal
recessive
or
dominant
http://www.blackwellpublishing.com/korfgenetics/figure.asp?chap=03&fig=Fig3-10
autosomal dominant
http://www.uic.edu/classes/bms/bms655/lesson7.html
http://www.uic.edu/classes/bms/bms655/lesson6.html
blood typing
IA _
A antigen
no B antigen
I B_
(HH)
H antigen
B antigen
no A antigen
ii
H antigen
no A or B antigen
h antigen
Bombay phenotype (hh)
no A or B or H antigen
http://anthro.palomar.edu/blood/Bombay_pheno.htm